The invention relates to an ink jet recording apparatus. More particularly, it relates to an ink jet recording apparatus for obtaining on recording paper, output images capable of meeting needs in a wide range from the printing business world in which the high speed output of a high quality image is required, to the printer industry which manufactures printers on the basis of office and personal requirements, as well as the consumer goods industry which manufactures inexpensive general-purpose output equipment employing various recording paper.
Shown in FIGS. 6 and 7 are examples of ink jet recording apparatuses which are used for an electrostatic acceleration type ink jet recording system in the conventional art.
Referring to FIG. 6, a slit 200 is formed by flat members 100 and 101, and it is filled up with ink 30. The ink 30 in the slit 200 undergoes a static pressure by ink 30 stored in an ink container 900, and it forms a semicircular convex surface, namely, a meniscus in the slit 200. An array of recording electrodes 40 is arranged on the inner surface of the flat member 101, while recording paper 50 and a counter electrode 60 are arranged at a position which confronts the recording electrode array 40 through a space. Each recording electrode of the recording electrode array 40 is connected at one end to the corresponding one of recording power sources 700, and is terminated at the other end in the vicinity of the slit-shaped ink jetting port 200. When a high voltage pulse is induced in any of the recording electrodes 40, the ink 30 existing near the specific recording electrode 40 flies toward the counter electrode 60 in the form of an ink droplet until it adheres to the recording paper 50 so as to form a pixel. Herein, the density of the recording electrodes 40 arrayed in the lengthwise direction of the slit 200 determines the line density of a recorded image. (Refer to Japanese Patent Application Publication No. 49189/1983.)
FIG. 7 is a perspective view showing the ink jet recording apparatus in the conventional art. Referring to FIG. 7, a plurality of recording electrodes 40 are disposed within a head. Ink is jetted by applying a voltage to a counter electrode 60 and selectively applying a high voltage only to the recording electrode 40 lying at a position nearest a desired ink jetting position so as to enlarge the potential difference of the specific recording electrode 40 relative to the counter electrode 60. Herein, the large number of electrodes 40 are arrayed dividing the space between an upper plate 12a and a lower plate 12b, so that openings 11 are formed at predetermined intervals. When ink not shown is poured into the openings 11, the electrodes 40 become wet with the ink. Therefore, the partitioned openings 11 are concealed, and the ink forms a continuous meniscus. When, in such a state, a high voltage pulse is impressed on the selected ones of the plurality of recording electrodes 40 while scanning these electrodes, ink droplets are jetted only from the vicinities of the positions of the selected recording electrodes. (Refer to Japanese Patent Application Publication No. 16825/1987.)
However, problems to be stated below are involved in the ink jet recording heads and the ink jet recording apparatuses which conform to the electrostatic acceleration type ink jet recording system in the conventional art.
In a case where the intervals of the plurality of recording electrodes disposed within the head are set sufficiently small in order to attain a high resolution, electric discharge is liable to occur across the adjacent recording electrodes due to the impression of the predetermined voltage pulse on the recording electrodes in a printing mode. Therefore, the voltage to be applied to the recording electrodes must be set lower than the voltage for jetting the ink. In consequence, the ink is not jetted, and the desired printing cannot be done.
Even with the construction wherein the plurality of electrodes are arrayed dividing the space between the upper plate and lower plate of the head so as to partition the openings, in the case where the intervals of the plurality of recording electrodes disposed within the head are set sufficiently small in order to attain a high resolution, the phenomenon of electric discharge similarly arises across the plurality of recording electrodes through the ink, and the desired printing cannot be done.
It is accordingly an object of the present invention to provide an ink jet recording apparatus in which, even when the intervals of a plurality of recording electrodes disposed within a head are set sufficiently small in order to attain a high resolution and when a predetermined voltage pulse necessary for jetting ink is impressed on the recording electrodes in a printing mode, the ink can be stably jetted without incurring electric discharge across the adjacent recording electrodes.
The present invention consists in an ink jet recording head having, at least, an opening; a supporting frame which forms a liquid chamber communicating with the opening and storing ink therein; a plurality of recording electrodes which are arranged near the opening; a counter electrode which is arranged at a position confronting the recording electrodes through a minute gap; and a power source circuit which applies a voltage across the recording electrodes and the counter electrode; characterized in that members having an electrically insulating property are arranged between the recording electrodes.
Further, the insulating members are arranged near the opening.
Still further, the insulating members are arranged in parallel with the recording electrodes on the supporting frame.
Yet further, the insulating members are arranged at a front end of the opening, and a region of the each insulating member is so shaped as to enlarge confronting the counter electrode.
In addition, the insulating members are arranged so as to lie nearer a front end of the opening than the recording electrodes, in the vicinity of the opening.
Besides, an ink jet recording apparatus according to the present invention consists in comprising the ink jet recording head; supply means for supplying the ink into the opening; a recording medium being arranged between the counter electrode and the opening; and a conveyance mechanism which conveys the recording medium.
In this manner, according to the present invention, the insulating members are disposed among the plurality of recording electrodes, whereby the electric discharge across the selected and non-selected ones of the recording electrodes is made less liable to occur. Thus, even in a case where the density of the recording electrodes in the head is set high in order to accomplish a high resolution, the ink can be stably jetted.